Conventional methods for manufacturing hexafluoroethane typically result in undesired impurities. Hexafluoroethane can be manufactured by fluorinating at least one of trichlorotrifluoroethane, dichlorotetrafluoroethane and/or chloropentafluoroethane. This hexafluoroethane manufacturing method often produces a product stream containing significant amounts of fluorocarbon and acid impurities which are difficult to remove by conventional distillation techniques.
Various gaseous fluorine-containing compounds are utilized to plasma etch silicon-type materials in order to fabricate semiconductor devices, e.g., A. J. Woytek, J. Fluor. Chem. 33, 331-334 (1986); the disclosure of which is hereby incorporated by reference. A major use of hexafluoroethane is as a plasma etchant in semiconductor device fabrication. It interacts with the surface of the integrated circuit wafer, modifying it so as to lay down the electrical pathways and providing for the surface functionalities that define the integrated circuit. As manufacturers are continually trying to increase the number of functionalities packed per unit surface area, the increasing fineness of surface detail in turn requires greater precision and consistency of the effect the etchant has on the wafer substrate. Products of high purity are critical for this application. It has been found that even very small amounts of impurities can result in wide line width and thus less information bits per chip. Moreover, the presence of these impurities, including but not limited to particulates, metals, moisture, and other halocarbons in the plasma etchant, even when present only in the part per million level, increases the defect rate in the production of these higher density integrated circuits. As a result there has been continually increasing market demand for higher and higher purity etchants, and an increasing market value for materials having the required purity. Consequently, identification of the offending impurities and their removal represents a significant aspect of preparing the fluorine-containing compounds for these applications.